Impact-driven conduit pipes and impact-driven survey monuments employing multiple interconnected sections are utilized when extensive distances must be traversed by such conduit pipes or survey monuments. Sectionalized, impact-driven survey monuments of the prior art may be typified by the survey monuments disclosed in the patents to Baumeister, U.S. Pat. No. 3,378,967, and Berntsen, No. 4,087,945. Similarly, sectionalized conduit driving mechanisms are found in the patents to McKenny, U.S. Pat. No. 1,894,446, and Marquiss, U.S. Pat. No. 1,210,187.
The Baumeister, Berntsen, and McKenney devices all are impact-driven mechamisms, while the Marquiss device is driven by means of a rachet jack mechanism. The devices of all of these patents employ sections of pipe or rods threaded together as they are driven vertically into the ground (as in the case of survey monuments) or horizontally under an area to be traversed (as in the case of the conduit driving devices). McKenney, Baumeister, and Marquiss all disclose external threads on hollow pipes and the use of conventional pipe couplers or, as in the case of Baumeister, the tube sections are inserted into one another by means of mating sleeve and socket extensions formed on opposite ends of each of the tube sections. In all of these devices, a penetrating tip is attached to the end of the first or forward marker or conduit section for penetration into the ground.
In the Marquiss device, a conical tip is threaded into the end section of the conduit to penetrate the ground and guide the remainder of the conduit sections as the sections are pushed by pressure of the jack through the ground. In Baumeister, a penetrating point is employed. In the McKenney and Berntsen devices, a similar penetrating point is threadedly attached to the end of the rod or pipe section entering the ground; and in both of these patents, the point has radially spaced, longitudinal, outwardly flared-barbs on the periphery of the point. These barbs additionally have a biassed turning surface to cause the points to rotate, along with the series of rods connected to the points, in a direction to tighten the threaded connections between the penetrating points and the rod section to which the points are attached, as well as to tighten the connections between all of the rods as the devices are driven into the ground.
The McKenney and Berntsen devices are substantially the same, except that in McKenny a hollow conduit is driven through the ground, whereas in Berntsen solid rods are driven into the ground. In the Berntsen device, a threaded connector is used to interconnect adjacent rod sections by threading the connector into threaded bores formed in the ends of each of the rod sections. This results in a smooth or uniform external surface of the interconnected rods. In McKenney an external pipe coupler is used to interconnect the sections.
Neither the Baumeister nor the Marquis devices rotate the rod sections, so that it is possible for the rod sections to loosen as the sections are driven into the ground. This is particularly true of the Baumeister device which is intended to be driven by a series of impacts or blows on the end remote from the penetrating point. The shock of these blows can loosen the interconnections. This is the reason the rotating points of the McKenny and Berntsen devices are employed. While the rotation imparted to the rod sections by the points of McKenny and Berntsen serves the purpose of maintaining the threaded connections screwed firmly together throughout the length of the pipe or rod, the use of a special separate point in both of these devices results in increased costs of the complete assembly. Furthermore by placing the outwardly flared barbs on the penetrating point itself, additional force is required to cause the penetration of the assembly into the ground. Also, the outwardly flared barbs can engage rocks or pebbles in the path of the marker or conduit and possibly deflect the true path desired for the monument or conduit as the assembly is driven through the ground.
Accordingly it is desirable to reduce the cost of rod sections of the general class described in the above patents and overcome the disadvantages of the McKenny and Berntsen devices caused by the specially constructed driving points, while retaining the advantages of rotating the rod sections in a manner to keep them tightly threaded together as the sections are driven into the ground.